There’s something I need to get off my chest. It’s been bugging me for about a year now ever since a good friend and colleague of mine, Dr. Julia Schultz, pointed it out to me while we were both postdocs at the University of Chicago and my mind kind of imploded.

“Propalinal” jaw movement is not a thing.

It’s a term that a LOT of people, including myself, have used to generally describe the jaw motions of certain herbivorous dinosaurs and other extinct critters, like dicynodonts and edaphosaurids. It describes a fore-aft motion of the jaw while the teeth are in occlusion. (Notice right off the bat that I said, “while the teeth are in occlusion”…This is important.) It is a combination of the word “proal” (which means a forward or rostral movement of the jaw while in occlusion) ad the word “palinal” (which means a backward or caudal motion of the jaw while in occlusion).

Now, these two terms, “proal” and “palinal” are completely valid. There is clear evidence for both of these.

In terms of proal motion, the main animals known to implement it are many proboscideans (yup, elephants push their food forward), rodents (in really, REALLY quick cycles), kangaroos, and the tuatara (Jones et al., 2009) — (yeah, that one surprises me, too, but it’s true!)

In terms of palinal motion, it seems, oddly enough, that the only animals that implemented PRIMARILY palinal motion are all extinct. These include multituberculates, haramyidans, and gondwanatherians (three non-therian mammal groups) (Schultz et al., 2014), dicynodonts (Angielczyk, 2004 – here termed “propalinal” but describing characters for a palinal motion), and, yes you guessed it, a LOT of herbivorous dinosaurs, primarily ornithischians (Mallon and Anderson, 2014; Varriale, 2016; Nabavizadeh and Weishampel, 2016). How do we know this? From tooth wear studies. All tooth wear studies that have been done have either shown proal or palinal motions, but never an indication of a “propalinal” motion. You always see a leading and a trailing edge of a tooth scratch, with no indication of a scratch going back and forth while in occlusion.

And if you think about it, it makes sense. In order to have a forward and backward motion of the jaw, you need more or less equal opposing muscle forces to effortlessly move the jaw forward and backward with the same amount of force. But lets look at what we really see: in rodents, we have a specialized muscle called zygomaticomandibularis that actually extends rostrodorsally toward the infraorbital foramen in many cases (especially hystricomorph rodents, like guinea pigs and capybaras) (Cox and Jeffery, 2011). This gives a clear rostrally-oriented vector for proal motion, which is what is seen in the tooth wear! In dinosaurs, most of the muscle are oriented caudodorsally (with a possible forward extension of muscle that will be described in an upcoming paper), with the exception of pterygoideus musculature, which is more for stabilization and slight translational rotations of the jaw and is not anchored rostrally enough to produce palinal motion. Pterygoideus muscles would also have been instrumental in the return vector for restarting a chewing cycle, but you don’t need nearly as much of a mechanical advantage and muscle force to do that). And guess what: their tooth wear only show palinal motion! Likewise, the musculature in dicynodonts and edaphosaurids would only produce palinal motion as well.

Why is it that the only animals that produce palinal motion are all extinct? I honestly can’t answer that confidently (although, I have some ideas), but it’s a great mystery to delve into. But the fact of the matter is, “propaliny” is just a term people (again, including myself) have used to describe a general uncertainty of forward or backward motion. And don’t get me wrong: it is totally fine in that context. But with knowledge of tooth wear now being a great resource, I suggest putting an end to this and picking which one it is — Proal or palinal? Because there is no microwear evidence to suggest “propaliny” in anything we know of (at least to my knowledge and to the knowledge of many I have talked to about this -– if you have differing info, please direct me to the source!) Until then, proal and palinal are two completely separate jaw motions. Lets treat them as such!

Cox, Philip G., and Nathan Jeffery. “Reviewing the morphology of the jaw‐closing musculature in squirrels, rats, and guinea pigs with contrast‐enhanced microCT.” The Anatomical Record 294.6 (2011): 915-928.

]]>https://anatomistsguide.wordpress.com/2017/06/09/propaliny-is-not-a-thing-its-either-proal-or-palinal-choose-wisely/feed/0anatomistsguideDSC_0370.jpgDinosaurs with Marionette Jaws: The Case for the Predentary in Ornithischianshttps://anatomistsguide.wordpress.com/2016/08/30/dinosaurs-with-marionette-jaws-the-case-for-the-predentary-in-ornithischians/
https://anatomistsguide.wordpress.com/2016/08/30/dinosaurs-with-marionette-jaws-the-case-for-the-predentary-in-ornithischians/#respondTue, 30 Aug 2016 06:25:46 +0000http://anatomistsguide.wordpress.com/?p=178Read More]]>As I mentioned in a previous post, ornithischian dinosaurs are enormously diverse. From the horned ceratopsians and dome-headed pachycephalosaurs to the armored stegosaurs and ankylosaurs and duck-billed hadrosaurs (and others), they make up a majority of the herbivorous non-avian dinosaur taxa to have ever lived. It’s a well-known fact that the presence of a single predentary bone at the front of the lower jaw is THE absolute dead give-away that a dinosaur is a member of Ornithischia; even better than noting their namesake “bird-like hip”. But have you ever wondered exactly why ornithischians had it in the first place? And, better yet, why is it that it persisted throughout ~140 million years of ornithischian evolution? This unique bone is largely unseen in a majority of vertebrates (other than very few convergences in fish, amphibians, and extinct birds), and yet this hugely diverse group of dinosaurs had it and kept it for their entirety.

I first started thinking about the enigmatic predentary bone for my undergrad senior thesis in 2008-2009. From then, I carried on looking into it as part of my PhD dissertation. I’ve been fascinated by both its huge diversity in shape as well as function throughout ornithischian groups. That’s what led to our new paper just out in Anatomical Record, “The predentary bone and its significance in the evolution of feeding mechanisms in ornithischian dinosaurs” (Nabavizadeh and Weishampel, 2016). It’s a good old-fashioned comparative anatomy project examining the form and function of this bone and its influence in the herbivorous lifestyles of these incredible creatures. My previous paper (Nabavizadeh, 2016) looked at the differences in mechanical advantage in the overall jaw structure across ornithischian taxa. Our new paper goes more in depth into the anatomy of the jaw as it relates to the predentary. What did we find? Well, there are actually (broadly) three types of predentary joints!
The first morphotype is the most simplistic, the predentaries resting against the front ends of the dentaries on each side of the jaw without much of a clasping, tight junction. A majority of the more basal ornithischians as well as basal ornithopods and ceratopsians, and it allows for very slight long-axis rotation of the lower jaw on each side of the mandible. The second morphotype involves the development of a symphyseal process (downturned front end of the dentaries) with a loosely attached predentary resting against or enveloping the dentaries, with a lot of wiggle room. Interestingly, this is convergently seen in hadrosaurs as well as ankylosaurs and stegosaurs and allows for a larger range of long-axis rotation. Lastly, the third morphotype involves a tightly clasping junction between the predentary and each of the dentaries, restricting any long-axis rotational movement. This is primarily seen in more advanced ceratopsians, especially the ceratopsids.

Why should you care? Well, we all like to think of many of these dinosaurs as enormous analogs to our present day herbivorous mammalian fauna, primarily due to the fact that they are “chewing” their food. But what we often don’t hear about is the fact that they are processing food in a completely unique way. In many of us mammals, do you notice how we usually chew on one side of the mouth at a time, with all the muscle forces from both sides focusing on that one bite point? Well, these dinosaurs were likely able to chew on both sides of the jaw at the same time, with the predentary sort of blocking the stresses from going to the opposite side of the jaw. In the cases of ankylosaurs, hadrosaurs, and ceratopsians, palinal feeding takes place, where the jaw is pulled backward during the feeding stroke. Additionally, ankylosaurs and hadrosaurs both incorporate a major component of long-axis rotation of the mandibles in addition to the palinal feeding stroke due to the loose connection of the predentary with the dentaries. This created a bolt-cutter-like mechanisms that would have been incorporated into their feeding, pushing vegetation straight into the mouth in every chew. Of course, this joint is formed by a fibrocartilaginous capsule, but this would allow some degree of rotation to occur. And, with the presence of a symphyseal process in the larger animals, the rotation of the mandibles at the front of the jaw are allowed to rotate much more freely and not separate during rotation, whereas more basal ornithischians without symphyseal processes would have this problem with too much rotation, although they still had wiggle room. The bigger you get, the more you need a way to rotate the dentary further in order to fulfill the feeding stroke. As for the ceratopsians, thy were primarily focused on orthal and palinal movements, but with their shearing tooth row morphologies, rotation of the mandible would not have been as necessary.

If it wasn’t for the predentary, the two dentaries would easily disarticulate with much rotation. The predentary would have acted as some sort of bracing axial point against which the dentaries could rotated and move around. Think of it as something like a marionette puppet, with multiple components forming the entire jaw with movement possible between each component. Various forms of a ball-to-socket jaw joint, a recurved coronoid process, and curved tooth rows also corroborate with these kinds of mechanisms; however, the greatest evidence of all has been with microwear studies that show us more and more about their paleoecology. It’s always super exciting to see data on tooth wear, and I’m looking forward to seeing more studies integrating all aspects of the feeding mechanisms to get the whole picture! Until next time!

Reference:

Nabavizadeh, A., and Weishampel, D. B. The predentary bone and its significance in the evolution of feeding mechanisms in ornithischian dinosaurs. The Anatomical Record. DOI: 10.1002/ar.23455

Link: http://onlinelibrary.wiley.com/doi/10.1002/ar.23455/abstract

~ Ali

]]>https://anatomistsguide.wordpress.com/2016/08/30/dinosaurs-with-marionette-jaws-the-case-for-the-predentary-in-ornithischians/feed/0anatomistsguideScreen Shot 2016-08-30 at 2.09.49 AM copy.jpgScreen Shot 2016-08-30 at 2.16.15 AM copy.jpgBenevolence in Science: Dr. Jack Conrad’s Legacy in Paleontologyhttps://anatomistsguide.wordpress.com/2016/07/25/benevolence-in-science-jack-conrads-legacy-in-paleontology/
https://anatomistsguide.wordpress.com/2016/07/25/benevolence-in-science-jack-conrads-legacy-in-paleontology/#respondMon, 25 Jul 2016 14:45:11 +0000http://anatomistsguide.wordpress.com/?p=170Read More]]>Many of us anatomists and paleontologists were completely and utterly shocked to learn that we lost a dear friend and colleague a few days ago, Dr. Jack Conrad. And, although I didn’t get to know him nearly as well as I wish I could have, it is so incredibly clear how much of a positive impact he has made in the lives of so many people in our field, particularly the younger rising paleontologists and anatomists.

I first met Jack at SVP in 2013. He walked up to a poster I was helping present and, right away, he was so incredibly encouraging, uplifting, and positive. It was seldom that I came across someone who was this encouraging of young scientists such as myself as I was becoming more acquainted with paleontological research. Jack exemplified what it truly means to be a great scientist in a community. He treated people with the utmost respect, class, encouragement, and humility. Best of all, he always had a smile on his face when he spoke to you. I am so deeply saddened that I did not have a chance to get to know him more or work with him. But I think there is something we can all learn from Jack’s time here.

Paleontologists tend to disagree with each other a lot. We’ve all been there. That’s science. You know what really matters, though? It’s not that you disagree and think that your way is the only way, but that you are scholarly, friendly, and positive in debating the subject at hand. We are in this field because it is FUN. Plain and simple. Yes, there is a serious side to it, but that serious side won’t get anywhere if all you do is put down someone’s research, either behind their back or to their face. There is nothing constructive about that. Be uplifting, be encouraging, and be constructive, especially to those younger than you in the field. It gives them hope and encourages them to do a lot better, maybe even if they aren’t starting off as well we they could be. That makes all the difference.

Jack did all of these things. He was among the absolute kindest people I have ever met in paleontology (aside from being an incredible researcher and illustrator). From the get go, he helped me feel welcomed and competent as a young paleontologist and he was one of the people who inspired me to strive to be kind and encouraging to all of the younger researchers who are just starting out. That is the number one thing that makes good scientists. It’s not how brilliant one may be, but how they treat others in their community with respect and positivity and strive to inspire others to be the best scientist they can be. In my mind, that is Jack’s true legacy in our field, and I will do my very best to live up to it.

]]>https://anatomistsguide.wordpress.com/2016/07/25/benevolence-in-science-jack-conrads-legacy-in-paleontology/feed/0anatomistsguideJaw Mechanics in Ornithischian Dinosaurshttps://anatomistsguide.wordpress.com/2016/01/19/jaw-mechanics-in-ornithischian-dinosaurs/
https://anatomistsguide.wordpress.com/2016/01/19/jaw-mechanics-in-ornithischian-dinosaurs/#respondTue, 19 Jan 2016 17:27:00 +0000http://anatomistsguide.wordpress.com/?p=158Read More]]>Ornithischia is a large and incredibly diverse clade including a majority of the megaherbivorous dinosaur subclades, except sauropodomorphs and few non-avian theropods. It included the horned ceratopsian dinosaurs, like Triceratops, the dome-headed pachycephalosaurs, the armored dinosaurs, like Ankylosaurus, the plated and spiked dinosaurs, like Stegosaurus, and the duck-billed hadrosaurs and their relatives. For well over a century, researchers have explored various aspects of the feeding apparatus of this immensely diverse clade, with studies examining osteological correlates of feeding motions, joint morphology and its impact on type and range of motion as well as jaw muscle reconstruction and mechanical advantage.

In my new study, “Evolutionary Trends in the Jaw Adductor Mechanics of Ornithischian Dinosaurs”, published online in the journal Anatomical Record, I present a broad scale analysis of jaw mechanics throughout 52 genera of ornithischian dinosaurs (spanning all subclades) to explore evolutionary convergences and divergences in mechanical advantage of the jaws throughout different points along the tooth row. Using 2D lever arm mechanics to do so, this study sheds light on variations in tooth row length, jaw length, and angle and mechanical advantage of the main jaw adductor musculature. It also investigates the effect of having a coronoid eminence or process and a jaw joint that is lower than the tooth row, both of which are features common in a majority of ornithischians.

Although the mechanical advantage is in the group containing stegosaurs and ankylosaurs were found to be much lower relative to the most other ornithischians, it is also worth mentioning how diverse their the mechanics of their jaws are amongst each other as well. All of these difference shed light on various aspects of variations in jaw mechanics throughout the clade. The most exciting finding throughout all of this study, though, is the convergent evolution of a significantly high increase in mechanical advantage of the jaws in the large ceratopsian dinosaurs like Triceratops and all of the duck-billed hadrosaurs (derived ornithopods), both of which exhibit large dental batteries with hundreds of teeth. The basal members of each clade are much lower in mechanical advantage, with both basal ceratopsians and basal ornithopods having similar mechanical advantage results throughout the tooth row. However, each group of derived members of the clade is significantly higher than their basal members, but not significantly different from the derived members of the opposite clade. This indicates clear convergence in increase mandibular mechanics in both ceratopsids and hadrosaurids, which likely is an effect of changing landscapes in the Cretaceous. Perturbation analyses also examine hypothetical jaw morphologies with no coronoid process and/or no lowering of the jaw joint, both of which are shown to impact the increase in moment arm length and, in turn, mechanical advantage.

The paper then explores how these jaw adductor mechanics in ornithischians effect various hypotheses in feeding mechanisms, providing more clues into the 140 millions year reign of these animals. Hopefully we can find out a lot more about these bizarre and amazing creatures! Hooray for ornithischians!!

]]>https://anatomistsguide.wordpress.com/2016/01/19/jaw-mechanics-in-ornithischian-dinosaurs/feed/0anatomistsguideCYibWX6WYAAGzqU“The Elephant’s Head” – Boas and Paulli Monographhttps://anatomistsguide.wordpress.com/2016/01/05/the-elephants-head-boas-and-paulli-monograph/
https://anatomistsguide.wordpress.com/2016/01/05/the-elephants-head-boas-and-paulli-monograph/#commentsTue, 05 Jan 2016 21:20:02 +0000http://anatomistsguide.wordpress.com/?p=93Read More]]>There is so much to say regarding the true beauty of the anatomy of living things and that is a large part of what this blog is meant for. I thought I might start off by showing some illustrations from my all-time favorite animal anatomy monograph.
Elephant facial musculature (Boas and Paulli, 1908)

This is Boas and Paulli’s “The Elephant’s Head”, published in two volumes (Volume 1 in 1908 and Volume 2 in 1925). Words cannot express how much this monograph has been an inspiration to me. Not so much because of the way it is written, but because of the hundreds of absolutely gorgeous illustrations it contains. A large part of my research entails craniofacial musculature of large mammals and this monograph is a large part of the reason why (it is mainly about elephant craniofacial anatomy, but also has descriptions and illustrations of many other mammals as well). The amount of incredible detail in illustrating the muscles (bellies/fiber direction) as well as bone, ligaments, and fascia is astounding and something I can only dream of aspiring to even creating a fraction of its beauty in my own research and illustration. I’ll let some of these example images speak for themselves (all from Boas and Paulli, 1908).
(Note: I’ll probably reference this monograph time and time again throughout my posts on this blog, so be forewarned.)

There is SO much more I could show you all. But in any case, this is one of the most important examples I can think of dealing with the great effect of integration of anatomy and illustration. It is something I hope we see a lot more of in the future of our field!

~ Ali

References:

Boas, J. E. V. & Paulli, S. (1908). The elephant’s head: studies in the comparative anatomy of the organs of the head of the Indian elephant and other mammals: Part I. Copenhagen: Folio, Gustav Fisher.

Boas, J. E. V. & Paulli, S. (1925). The elephant’s head: studies in the comparative anatomy of the organs of the head of the Indian elephant and other mammals: Part II. Copenhagen: Folio, Gustav Fisher.

Hadrosaurs (a.k.a., the ‘duck-billed dinosaurs’) never really get the attention they deserve. Why? Well, probably because they don’t really have much in the way of cool spikes, armor, horns, or knife-like, serrated teeth as other dinosaurs do. They are many times referred to as the “Cows of the Cretaceous”, which, quite frankly, I disagree with entirely. Not that I don’t think cows are interesting in their own right, but hadrosaurs have so many other fascinating aspects of their biology that boggle the minds of paleontologists around the world. It’s hardly fair to compare them. Here, I am going to talk about a particular hadrosaur adaptation that has puzzled paleontologists most of all, for over a century: their crazy, tooth-infested feeding apparatus.

A few months ago, I was lucky enough to have my paper entitled, “Hadrosauroid Jaw Mechanics and the Functional Significance of the Predentary Bone” published as a chapter in an Indiana University Press compilation volume by David Evans and David Eberth called “Hadrosaurs“. In it, I discuss the anatomy of jaw elements in a few different hadrosaur genera to understand, qualitatively, how different elements were able to move against each other during feeding and what this meant for the entire jaw mechanism as a whole.

“Hadrosaurs” volume, edited by David Evans and David Eberth. Cover art by Julius Csotonyi.

Hadrosaurs have a lot of teeth. I mean, a LOT of teeth. About 1,400 of them. They are stacked up on each other in up to around 40 columns and they continuously grow new ones throughout their lifetime. What’s even more interesting, though, is how they are oriented and associated with each other. The columns of teeth are pushed together from front to back (mesial to distal, for the jaw scientists out there) and, at the occlusal surface, they combine to form an elongate, flat surface on which the opposing jaw can bite. This huge platform occlusal surface gives room for it to move in different directions while chewing. Furthermore, the elongate combined occlusal surface of the lower teeth angle outward (i.e., toward the outside of the mouth) while the occlusal surface of the upper teeth are angled inward toward the tongue. This creates an angled occlusion, which would make it seem like the food would fall right out of the mouth.

A hypothesis of hadrosaur feeding mechanisms that was well accepted for over two decades, was proposed by my previous PhD mentor, Dave Weishampel (1984), as well as David Norman (1984) called “Pleurokinesis” (also see: Norman and Weishampel, 1985). Pleurokinesis is a feeding mechanism involving a domino effect of cranial elements causing the upper jaw, or maxilla, to rotate outward during occlusion while the lower jaw closed upward. This was proposed for various reasons, including mobility at certain joints within the skull as well as tooth wear that was oriented transversely, which was unusual for an animal with an occlusal surface that is angled outward. Recently, Pleurokinesis has been rejected by a few studies based on restrictions of cranial elements by other cranial elements, ligaments, and muscles (Holliday and Witmer, 2008; Rybczynski et al, 2008; Bell et al., 2009; Cuthbertson et al; 2012).

Now, the dentary should be a more familiar bone for most anatomists and paleontologists. It is the largest bone in the lower jaw. A bone that might not be as familiar to many, however, is the predentary bone. The predentary bone is a single, midl).ne element that articulates with the front end of the dentary bones on either side, creating what is, functionally, the animal’s chin. With very few exceptions, predentaries are mainly only found in ornithischian dinosaurs, which include the horned ceratopsians, plated stegosaurs, armored ankylosaurs, dome-headed pachycephalosaurs, and billed ornithopods (including hadrosaurs) as well as their kin. Exactly what is this bone used for? Why did ornithischians evolve it and keep it for over 100 million years of evolution

The question still remains, though: how DID hadrosaurs “chew” with this tooth morphology? In my analysis of hadrosaur jaw bones, I tried to find out exactly how the bones articulated with one another and if there was potential movement between bones that maybe have not been emphasized before. The studies that rejected pleurokinesis briefly discussed potential mobility at a joint that was not thought of much before: the predentary-dentary joint, although there were no predentaries available in their analyses.

Hadrosaur predentary in different views. Figure from Nabavizadeh (2014).

In this paper, I discuss the possibility that the predentary bone likely acted as an axial point at the midline as the two dentaries rotated around their long-axes simultaneously during “chewing”. One way they were likely capable of doing so is the lack of a clasping junction between the dentaries and predentary. Look at any museum specimen of a hadrosaur on display and you’ll see that it is really just hovering in front of the jaw with no clear connection with the rest of it. Funny, isn’t it?

What does this mean? Well, it was probably rotating around slightly in a fibrocartilagenous joint capsule at the predentary-dentary junction. Remember, too, that it wouldn’t need to rotate around much at the front of the jaw to create a much larger rotation toward the back of the jaw with the angle they are associated in. Other aspects of the anatomy that suggest this rotation are the ball-to-cup articulation of the cranium with the jaw at the quadrate-articular jaw joint (how could it not be rotating??) as well as the tooth wear orientations showing multi-directional wear.

Proposed long-axis rotation of both sides of the jaw. Figure from Nabavizadeh (2014).

With this analysis, I suggest a feeding mechanism that starts with a front to back palinal chewing motion followed by a “bolt-cutter-like” cutting of vegetation rotating into the mouth on both sides of the jaw simultaneously. This type of feeding mechanism would have been difficult without the aid of another bone such as the predentary to keep the jaws together. Just another example of how wonderfully bizarre hadrosaurs really are.

All of this isn’t to say that there is a lot more involved in hadrosaur jaw mechanics than just how their bones are put together. There are so many other important factors in hadrosaur feeding, not the least of which is their crazy jaw musculature. This study specifically opens up a lot of questions as to the function of the predentary bone in ornithischian dinosaurs as a whole and why it’s so important. My dissertation expanded upon this and other scenarios in ornithischian feeding, so more papers will be coming your way soon! Stay tuned.

]]>https://anatomistsguide.wordpress.com/2016/01/05/hadrosaur-jaw-mechanisms/feed/0anatomistsguideScreen Shot 2015-05-07 at 10.10.16 AMScreen Shot 2015-05-07 at 10.17.24 AMScreen Shot 2015-05-07 at 10.17.16 AMScreen Shot 2015-05-07 at 10.17.04 AMScreen Shot 2015-05-07 at 10.17.33 AMA Little Introductionhttps://anatomistsguide.wordpress.com/2016/01/05/a-little-introduction/
https://anatomistsguide.wordpress.com/2016/01/05/a-little-introduction/#respondTue, 05 Jan 2016 04:38:19 +0000http://anatomistsguide.wordpress.com/?p=8Read More]]>Hey everyone! My name is Ali Nabavizadeh and I’m a postdoctoral scholar in Organismal Biology and Anatomy at the University of Chicago teaching medical gross anatomy and the Pritzker School of Medicine. I received my PhD in Functional Anatomy and Evolution at the Johns Hopkins University School of Medicine in 2014.

I am interested in all things integrating comparative vertebrate anatomy, biomechanics, paleontology, and scientific illustration. Although my dissertation investigated the biomechanics of jaws in ornithischian dinosaurs, my interests have broadened widely to dissection and anatomical / biomechanical investigation of everything from large living mammals, like rhinos and elephants, to small birds and reptiles. I am also interested in reconstructing musculoskeletal anatomy in extinct relatives of these taxa based on similar osteological correlates. I do this with the help of training I acquired through taking courses with the Art as Applied to Medicine Department at Johns Hopkins, which greatly helped me hone my artistic capabilities and integrate it into my research.

The purpose of this blog is to follow my growing path as a comparative and human anatomist, in both research (dissection and biomechanics) and education, and to emphasize the importance of scientific and medical illustration into anatomical and biomechanical research and education. Along the way, I hope to invite many of my colleagues to join me in contributing to this blog as well, whether they be anatomists, paleontologists, zoologists, or scientific / medical illustrators alike!